Last month, the United States Department of Agriculture announced a recall of all cattle slaughtered at the plant on a single day in January; on Saturday, a second recall was initiated for a year’s worth of beef, totaling approximately 8,742,700 pounds. U.S.D.A. inspectors maintain Rancho processed “diseased and unsound” animals that received only a partial inspection or were not examined at all, rendering the meat “adulterated” and “unfit for human food.”

The recall will likely have devastating economic effects since many ranches in West Marin slaughter their grass-fed beef seasonally and freeze the meat to release at scheduled intervals. With most recalls, the meat has already been sold to customers and only a small portion is expected to be returned, but in Rancho’s case, hundreds of thousands of dollars of meat have never been distributed and will need to be reimbursed out of pocket, clients said.

“I have at least 200 customers that received beef last year. I have to review my records and now I have to send out a letter to each of them,” said Mike Gale, a co-owner of Chileno Valley Ranch. “It’s a very time-consuming and frustrating exercise to say the least. There’s no direct link to any meat being a problem for those who have consumed it over the last year.”

Mr. Gale said he would personally have to drive to pick up any meat across the Bay Area and the state from Fort Bragg to San Diego, a process he called “ridiculous” and “just impossible.”

In a letter to producers, Rancho’s manager Scott Parks said, “Your prompt action will greatly assist Rancho Feeding Corporation in this action.”

On the advice of their lawyers, the plant’s management declined to comment on the U.S.D.A.’s allegations, instead issuing a statement, saying the plant is voluntarily recalling the meat “out of an abundance of caution.” “Rancho Feeding Corporation deeply regrets any inconvenience this may cause to our customers,” the statement added.

Technically, all recalls are undertaken “voluntarily,” since the company is not obliged to remove their own product from the market. However, recalls are often “volunteered” by a firm as an alternative to a product’s detention or seizure by U.S.D.A. But if Rancho had refused, they would have had the option to challenge any administrative action in the courts, said Gary Cox, co-founder and general counsel for the Farm-to-Consumer Legal Defense Fund.

“If the recall is voluntary, U.S.D.A.’s actions do not come into question, and there is no judicial review,” he said. “If it were me, and I did not receive satisfactory explanation from U.S.D.A., I wouldn’t voluntarily agree to one.”

Neither U.S.D.A. nor Rancho Feeding has received any reports of illnesses associated with the meat. A recall does not imply that all of the meat is unsafe for consumption; it is taken as an added precaution to protect the public.

In Rancho’s case, the recall could have been initiated because a step in a rigorous inspection process may not have been completed, or even properly documented. Prior to slaughter, inspectors observe the animals at rest and in motion for signs of illness, and they watch the employees for humane handling, documenting any violations from clearly abusive treatment to sufficient levels of water in the pens. They are present inside the facility to witness the slaughter and to check each carcass individually. Any misstep from procedure renders the meat adulterated.

Stacy Kish, a U.S.D.A. spokeswoman, said she could not elaborate on the agency’s basis for believing “diseased and unsound” animals were slaughtered. Uninspected meat could have been placed in boxes bearing the U.S.D.A. seal because they are pre-stamped, she added.

The recalled beef products were distributed in California, Florida, Illinois and Texas. They include almost any edible part of the cow—from the carcass, which is later butchered into the familiar cuts you find at a grocery store, to the offal, including the head, the small intestine known in Mexican cuisine as tripas, the testicles known as “Mountain Oysters,” various edible glands known as “Sweet Breads,” the liver, tongue, feet and hearts. Veal cuts, bones and trim were also recalled.

This recall is the second largest of the past year, surpassed only by an open federal case investigating 10.5 million pounds of frozen meals and snack items suspected of E. coli contamination recalled last April. It is also the largest amount of product recalled in recent years due to incomplete inspections. The closest in size was an order of magnitude smaller: a September recall of 170,000 pounds of ravioli produced in Oregon without any inspection.

Beyond U.S.D.A.’s allegations, little else is clear, leading to suspicion among Rancho’s patrons about the need for a recall of high-quality beef.

Most beef ranchers take their cattle to the plant for custom processing, meaning they pay Rancho only to slaughter their cows. These ranchers then sell the product to customers or wholesalers. For retired dairy cows, on the other hand, Rancho often purchases the cattle, slaughters them and sells the meat, often as ground beef. The dairy and beef cows are slaughtered on separate days to prevent meat being mixed, clients said.

While beef farmers can testify to the quality of their stock, the dairy ranchers who are culling the undesirable parts of their herd often bring a lower-quality product. Last fall, testing of two cows from a northwestern Nevada dairy slaughtered at Rancho revealed penicillin levels in the kidneys at 30 and 68 times the federal limits.

U.S.D.A.’s blanket recall fails to recognize the careful oversight of their herds, beef ranchers said, and casts suspicion on an otherwise safe product.

“Each week, we hand-pick the best of the best animals to be harvested. Our reputation depends on high quality,” said Loren Poncia, of Stemple Creek Ranch. “We stand behind our product 110 percent, and feel good about feeding it to our own children and family. The North Bay is known for raising some of the best grass fed been in the nation.”

Some customers have also rallied in support, saying they trust their local farmers.

“We had a Stemple Creek tenderloin for Christmas, and we’ve been eating True Grass ground beef on our Tuesday taco nights at my home all year,” said Gibson Thomas, the publisher of the quarterly magazine Edible Marin & Wine Country. “To compare any of this to factory-raised beef is wrong. This is so wildly different from the vast majority of meat we eat in our country, and we need to give our local ranchers credit and support.”

Local producers have found the news hard to swallow because the very existence of local alternative meat production is at risk. Without a viable slaughterhouse in the area, producers will need to truck cattle as far away as the north end of the Central Valley, undoing the idea of local agriculture. Rancho’s closure does not simply mark the death of a slaughterhouse; it means the defeat of an ideal.

In 2008, Tara Smith and her husband, Craig, were working in the insurance business when their son brought home Michael Pollan’s “The Omnivore’s Dilemma: A Natural History of Four Meats.” The book diagnoses America with an unhealthy eating disorder, drawing attention to its dependence on industrial agriculture, epitomized by endless cornfields in Iowa and teeming feedlots in Kansas. In the spring of 2009, they bought 290 acres just south of Petaluma in the hopes of finding their own methods of producing and eating ethically.

Ms. Smith lost six of her cows during the initial raid in January, and says the costs from both recalls will be at least $8,000. “They don’t want us here. They don’t want the little farms. They don’t want organic. They don’t want local people growing local food,” Ms. Smith said of the U.S.D.A.

If Rancho shuts down permanently, Ms. Smith said she will likely close, too. For one, she can’t afford the costs of trucking her animals far away, and even if she could, she wouldn’t subject her animals to it to the torturously long drives.

She said Rancho has always been “spit-spot” clean, and she trusts the workers there whom she’s know for years.

“I got into this business to serve up healthy, clean food. I put my animals out onto pasture and complete that life cycle,” Ms. Smith said. “I wouldn’t be willing to send an animal down to Fresno to be part of that mess. It would break my heart. If Rancho goes away, so do we.”

Additional reporting by Robin Carpenter